> 
i sted: in the bed of this ancient sea, and such some of the - 
‘strata over portions of country which can be examined con- . 
‘and from intermixture of mechanical deposits as well as other | 
" Le f Ba 
18 Hall on the Strata and ganie Remains 
tion of this c tinent, during the | mo of the a lime- 
ne beds of the Mississippi valley. 
LA New York we find every one of our limestone formations 
succeeded by a deposit of mud, which would put an end to all | 
growth in the corals, t times it it appears that this mud 
was rapidly accumulat 
This immense ocean was evidently margined on the east by 
a continent which supplied all the detritus. forming the me- 
chanical deposits; perhaps by the influx of mighty rivers, - 
bringing down mud and sand ; that during some periods there _ 
was a cessation of these ‘deposits, and at the same time the — 
calcareous formations were preserved, with their infinite variety i 
of organic forms. The influence of these mud deposits and — 
turbid waters did not however, extend throughout the whole D, 
area ; and beyond their reach, the corals of various kinds, the 1 
Guides, and many other beautiful forms flourished in secu- 
rity, while iey were prevented from extending TONS their 
. Such sails appear to havilibeon 1 the collditions which ex- 3 
causes which have influenced the distribution of organic re- 
mains, over its bed, during the period of the Silurian or 
New York system. 
If we find such changes in the nature and condition of the 
eiae agat. 
tinuously, what may we not expect should we undertake to 
compare rocks of the same age when separated by three thou- 
sand miles of ocean? It is very plain, that all mechanical de- — 
posits must essentially change, when traced over such great i 
us deposits, , also, whether supplied from — 
Orals, must essentially change in devel- 
opment or condition, both fra inequalities in the ocean be bed, 
a 
causes. Since, also, we find a considerable variation in th 
aspect and contour of the same o of Rei at. Vene 
